This invention relates to a thermal transfer printer, and, more particularly, to a thermal transfer printer in printing with the ink ribbon in plural columns at align winding of the ink ribbon.
A disadvantage of an ink ribbon used in a conventional thermal transfer printer resides in the fact that, because ink of the ink ribbon is completely transferred to a thermal transfer printing paper in only one printing and can not be reused, the ink ribbon increases the overall operational costs of the printer.
To avoid the above noted disadvantage, a thermal transfer printer is proposed in Japanese Utility Model Laid-Open No. 194042/1983. Wherein the thermal transfer printer has a reversing mechanism for reversing a driving direction of an ink ribbon and also a vertical movement mechanism for a thermal head whereby it is possible to print in both the forward and backward directions with two columns, that is, upper and lower tracks of the ink ribbon. However, this thermal transfer printer becomes structurally complex because both a reversing mechanism of the ink ribbon and the vertical movement mechanism of the thermal head are necessary.
Furthermore, to reciprocatingly print, the moving distances of the ink ribbon to go and return must be equal, so the ink ribbon can not stop moving in the space not to print in the same one line of the ink ribbon, and such fact is not economical in considering a consumption of the ink ribbon.
So, when printing of the thermal transfer printer is carried out in a pair of upper and lower columns of the ink ribbon only by the reverse mechanism of the ribbon cassette without both the reverse mechanism in driving direction of the ink ribbon and the vertical movement mechanism of the thermal head, etc. in the thermal transfer printer itself, the thermal transfer printer can print the same method as a unidirectional printing method.
And effective length of used ink ribbon in the thermal transfer printer can be twice of previous one, so that a lower operating cost can be realized by the user of the thermal transfer printer.
However, there are no documents about the techniques for the ink ribbon winding of the thermal transfer printer in a regular or aligned state under the conditions of shifting down or shifting up in the ink ribbon, and that is important problem in the case of printing in plural columns such as upper and lower two columns using same one ink ribbon.
An object of the present invention is to provide a thermal transfer printer for printing in plural columns with one ink ribbon wherein the shift-up or shift-down of the ink ribbon at a thermal head can be prevented.
An another object of the present invention is to provide a thermal transfer printer for printing in plural columns with one ink ribbon wherein winding of the ink ribbon can be carried out in an aligned raw.
A further object of the present invention is to provide a thermal transfer printer for printing in plural columns with one ink ribbon wherein winding load of the ink ribbon can be decreased.
A still further object of the present invention is to provide a thermal transfer printer for printing in plural columns with one ink ribbon wherein wind-uncapable accidents of the ink ribbon can be prevented.
Yet another object of the present invention is to provide a thermal transfer printer for printing in plural columns with one ink ribbon wherein winding tension of the ink ribbon can be made small.
According to the present invention, a thermal transfer printer is provided which includes a thermal head, a platen roller pressed against the thermal head through a thermal transfer printing paper, a carriage mounted with the thermal head and a ribbon cassette and transversely moving along the platen roller, and an ink ribbon having plural columns and being received within the ribbon cassette. A center of a flat portion is formed on the platen roller of a contact portion of the thermal head and a center of the thermal head are shifted corresponding to an amount of shift of printing position as against a center of width of the ink ribbon.
The thermal transfer printer of the present invention provides a structure wherein the center of the thermal head is set above a width of the flat portion formed on the platen roller of the contact portion of the thermal head, when the printing position is set above as against the center of width of the ink ribbon, or a structure of the center of the thermal head is set below width of the flat portion being formed on the platen roller of the contact portion of the thermal head, when the printing position is set below as against the center of width of the ink ribbon.
The present invention can prevent the shift-up or the shift-down of the ink ribbon at the thermal head in structure in which the center of the ink ribbon width and the center of the printing shift in the plural columns printing.
Only the central part of the ink ribbon is used for printing in the conventional thermal transfer printer. On the other hand, when the structure of the thermal transfer printer for printing in plural columns, such as upper and lower columns, with one ink ribbon is used for smaller consumption of the ink ribbon, the following technical problems arise.
In the conventional thermal transfer printers, the center of one ink ribbon is printed, but in the case of plural columns printing, such as upper and lower columns, printing the center of ink ribbon width and the center of printing are not coincident. Consequently the stress distribution acted on the ink ribbon in the running ink ribbon differs at upper and lower parts of the ink ribbon, so a rising (shifting up) phenomena or a sinking (shifting down) phenomena of the ink ribbon at the thermal head is occurred.